1. Technical Field
Methods of forming metal wires of semiconductor devices are disclosed, and more particularly, methods of forming such metal wires which can reduce junction leakage current caused by a reduction of the current resistance and can improve the reliability of the semiconductor device by adding the same dopant as that of a lower junction layer on the surface of a bit line contact before the deposition of the titanium film or the titanium nitride film. As a result, the diffusion of the dopant in the junction area consumed through heat treatment in the formation of the titanium silicide film is maximized and the contact resistance caused by the increase in the concentration of the dopant in the junction area is improved.
2. Description of the Related Art
Generally, as the integration of a semiconductor device increases, the depth of a junction area and the size of the contact hole decrease. Therefore, it becomes difficult to adequately fill the contact hole in metal contact process. Thus the contact resistance is increased and the electrical properties of the device are deteriorated.
To solve this problem, a barrier metal layer containing titanium silicide (TiSi2) is formed on the base of a contact hole by depositing titanium (Ti) and titanium nitride (TiN) and performing heat treatment thereon. In addition, with high integration of a semiconductor device, the formation of a metal wire having a low resistance is required. As materials of the metal wire, tungsten (W), aluminum (Al), titanium (Ti), cobalt (Co), zinc (Zn), copper (Cu), silicon (Si), platinum (Pt), aurum (Au) and the like are used. Among them, to reduce the fabrication cost, tungsten and aluminum are mainly used as they have a relatively low resistance and are easily deposited.
However, the more the device is integrated, the smaller the concentration of ions existing in the junction area. Thus the resistance of the metal wire increases gradually. Also, the contact area is reduced by the reduction of the contact size. This generates an additional problem increased contact resistance.
FIG. 1 is a cross-sectional view showing a method of forming a metal wire of a semiconductor device according to the conventional art.
Firstly, as illustrated in FIG. 1, an interlayer insulating film 12 is formed on a semiconductor substrate 10 in which a junction area 11 is formed. A contact hole is formed by etching a selected portion of the interlayer insulating film 12 to expose the junction area 11. Next, for electrical insulation with peripheral devices, a spacer insulating film 13 is formed on a side wall of the contact hole.
A metal barrier layer 16 is continuously formed by sequentially forming a titanium film 14 and a titanium nitride film 15 on top of the interlayer insulating film 12 including the contact hole by the sputtering method. Thereafter, a titanium silicide film 17 is formed on the base of the contact hole by carrying out the rapid thermal process (RTP) at an atmosphere of nitrogen (N2) or ammonium (NH3) gas. This titanium silicide film 17 is formed by the interaction between silicon atoms (Si) of the semiconductor substrate 10 and titanium atoms (Ti) of the titanium film 14 during the rapid thermal process.
Next, a tungsten layer 18 is deposited on the titanium nitride film 15 constituting the metal barrier layer 16 by the chemical vapor deposition (CVD). A metal wire (not shown), is formed by patterning this tungsten layer 18.
However, in the above-described conventional method of forming the metal wire or contact, the titanium silicide film 17 is formed on the interface between the titanium film 14 of a metal layer and a silicon semiconductor substrate 10. Accordingly, B+ ions are diffused into the metal layer and the B+ dopant in the metal-silicon interface is reduced, thereby increasing the resistance.
Therefore, methods of forming metal wires or contact of semiconductor devices are disclosed which reduces the junction leakage current caused by the reduction of the current resistance and which improves the reliability of the semiconductor device by maximally depressing the diffusion of the dopant in the junction area consumed through heat treatment in the formation of the titanium silicide film and further which improves the contact resistance caused by the increase of the concentration of the dopant existing in the junction area.
One disclosed method of forming a metal wire of a semiconductor device comprises: forming an interlayer insulating film on a semiconductor substrate in which a junction area is formed; forming a contact hole to expose the junction area by etching the interlayer insulating film; forming a spacer insulating film on a side wall of the contact hole and adding the same dopant as that of a lower junction layer including the junction area; forming a metal barrier layer by sequentially depositing a titanium film and a titanium nitride film on the interlayer insulating film including the contact hole; forming a titanium silicide film on the resultant material having the metal barrier layer; and forming a metal wire by forming a tungsten layer on the titanium nitride film and patterning the tungsten layer.
Preferably, the titanium silicide film is formed by the rapid thermal process, and the tungsten layer is formed by the CVD method.
Preferably, addition of the same dopant as that of the lower junction layer and forming the titanium film and the titanium nitride film are carried out in-situ. The forming of the titanium nitride film on the titanium film is carried out in-situ after adding the same dopant as that of the lower junction layer and exposing the same to air for a predetermined time and then is deposited in-situ.
Preferably, the titanium silicide film is formed by performing the rapid thermal process at an atmosphere of nitrogen (N2) or ammonium (NH3) gas. The adding of the same dopant as that of the lower junction layer is carried out using the CVD plasma treatment or the rapid thermal process. At this time, the CVD plasma treatment is carried out over a time period ranging from about 1 to about 60 minutes at a temperature ranging from about 350xc2x0 C. to about 800xc2x0 C. using a RF power ranging from about 0.5 kW to about 5 kW.
Preferably, when adding the same dopant as that of the lower junction layer by the CVD plasma treatment, one of gases selected form B2H6 gas, PH3 gas, and BF3 gas is used as a processing gas. The step of adding the same dopant as that of the lower junction layer using the rapid thermal process is carried out over a time period ranging from about 60 seconds to about 60 minutes at a temperature ranging from about 650xc2x0 C. to about 800xc2x0 C. using a RF power ranging from about 0.5 kW to about 5 kW.
Preferably, when adding the same dopant as that of the lower junction layer using the rapid thermal process, one of gas selected form B2H6 gas, PH3 gas, and BF3 gas is used as a processing gas.
In accordance with another embodiment, a method of forming a metal wire of a semiconductor device comprises: forming an interlayer insulating film on a semiconductor substrate in which a junction area is formed; forming a contact hole to expose the junction area by etching the interlayer insulating film; depositing a titanium film on the interlayer insulating film including the contact hole; forming a spacer insulating film on a side wall of the contact hole and adding the same dopant as that of a lower junction layer including the junction area; forming a metal barrier layer by sequentially depositing a titanium nitride film on the titanium film added the same dopant as that of the lower junction layer; forming a titanium silicide film on the resultant material having the metal barrier layer; and forming a metal wire by forming a tungsten layer on the titanium nitride film and patterning the tungsten layer.